Effect of decision confidence on the evaluation of conflicting decisions in a social context

Conflicts with others about decisions are reflected in the medial frontal negativity (MFN), which is a component of the event-related brain potential (ERP). The present study examined how decision confidence in a perceptual decision task modulated the ERP components elicited by decision conflicts with others. In a motion discrimination task, participants were randomly assigned to an easy or a difficult group that differed in coherence levels of the moving dots. Participants were paired with a confederate and presented the confederate's decision about the motion direction of the moving dots, which was either congruent or incongruent with the participants' decision. MFN was elicited by the incongruent confederate's decision and its amplitude did not differ between groups. A larger P300 amplitude was elicited by incongruent decisions in the easy group, whereas the P300 amplitude did not differ between congruent and incongruent decisions in the difficult group. These results indicate the functional dissociation between MFN and P300 in the evaluation of social feedback. It is suggested that MFN might reflect automatic detection of conflicts about decisions, whereas the P300 might detect the deviation from internal expectations regarding other's decisions.